Veterinary Medicine - June 2008 - (Page c8)

Porcine insulin zinc suspension in the management of feline diabetes mellitus Linda J. I. Horspool, BVMS, PhD, DECVPT, MRCVS International Technical Manager Companion Animals Intervet International bv Vetsulin (porcine insulin zinc suspension) is approved by the FDA for reducing hyperglycemia and hyperglycemia-associated clinical signs in cats with diabetes mellitus. Internationally, it was rst approved for use in the early 1990s and is registered for dogs and cats as Caninsulin in more than 30 other countries. Vetsulin is supplied as a sterile injectable suspension in multidose vials of either 2.5 ml or 10 ml of 40 U/ml (U-40) porcine insulin zinc suspension.Vials are supplied in cartons of one 10-ml vial and cartons containing ten 2.5-ml vials. Vetsulin should be administered using a U-40 insulin syringe. Use of a syringe other than a U-40 will result in incorrect dosing.Vetsulin should be kept refrigerated. It is good clinical practice to replace opened vials on a monthly basis. Species differences in insulin Pork insulin is a protein composed of 51 amino acids, arranged in two chains (an acidic A chain and a basic B chain) cross-linked by disulphide bridges.1 The amino acid sequence of insulin is highly conserved among vertebrates, with little variation in the amino acid sequence of the 21 amino acid A chain and the 30 amino acid B chain. Pork insulin has the same A-chain structure as canine and human insulin but di ers slightly from feline insulin, as shown in Table 1 (page 10). Pork insulin has the same B-chain structure as canine, feline, and bovine insulin but di ers slightly from human insulin, as shown in Table 1. Insulin from one mammal is biologically active in another. All mammalian insulins, irrespective of species origin, bind with a similar a nity to insulin receptors at the three sites of action—muscle, adipocyte, and hepatocyte—and initiate post receptor events in terms of autophosphorylation.2 Pork insulin is used e ectively and safely in long-term human, canine, and feline cases. Di erences in amino acid structure of insulin from di erent species result in slightly di erent solubility, which in turn a ects activity. For example, pork and beef zinc insulin crystals are more fat soluble than human zinc insulin crystals and, therefore, cross the blood-brain barrier more readily than human insulin. In practice, although patients on animal derived insulins may theoretically be aware of the onset of hypoglycemic episodes earlier, this di erence is not completely clear. Insulin pharmacokinetics and pharmacodynamics The healthy pancreas secretes endogenous insulin as monomers (single molecules) from the beta cells of the islets of Langerhans. In contrast, exogenous insulin, for subcutaneous injection, consists of complex hexamers (complexes containing six subunits) that are broken down into monomers and dimers (molecules with two similar subunits) after subcutaneous 8

Table of Contents Feed for the Digital Edition of Veterinary Medicine - June 2008

Veterinary Medicine - June 2008 Contents Leading Off Clinical Exposures Idea Exchange A Challenging Case: Conjunctival Lymphoma in a Cat Updates on Canine Hypoadrenocorticism Product Preview CE Form Advertiser Index Marketplace/Classifieds Mind Over Miller Clinical Edge - June 2008 Table of Contents Managing Diabetes Mellitus in Cats: What Makes it Work? Porcine Insulin Zinc Suspension in the Management of Feline Diabetes Mellitus Monitoring Diabetes Mellitus in Diabetic Cats Feline Diabetes Mellitus: Important Client Communication Points

Veterinary Medicine - June 2008

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